Modified pitch



Patented Nov. 1, 1938 UNITED STATES PATENT OFFICE MODIFIED PITCH No Drawing. Application December 17, 1935, Serial No. 54,852

4 Claims.

This invention relates to the production of a residual pitch of vegetable or animal origin, so highly modified by oxidation, and by the addition of another oxidized ingredient, compatible 5 with the pitch, that it is rendered useful in the manufacture of mastic tile, as an ingredient of a protective coating composition for use in protecting ships bottoms, and various structural materials, and which maybe considered generally as useful in making up various compositions in which it is desirable to incorporate an elastic ingredient, having bonding qualities, and which may readily be pigmented.

Vegetable pitches occur as a residuum in the refining of the various vegetable oils, cottonseed pitch being the best known example of this class of pitches. In refining animal fats, fish fats, and to some extent in refining vegetable fats, stearin pitches are also obtained as-a residual product. These pitches, when oxidized, have been used with coumarone resin and with asphalt to provide the elastic ingredient of mastic tiles, and, to some extent, to provide a paint base. The admixture of these pitches with coumarone resin gives for purpose of tile manufacture a composition which is relatively expensive, and which is deficient in the quality of elasticity. While a mixture of one or more of the pitches with asphalt gives a composition more elastic than that obtained by admixture with coumarone resin, it is not highly elastic, has a relatively low meltingpoint, and is of such dark color, in solution and in a film as well as in mass, that it is either incapable of pigmentation by pigments of the lighter shades, or requires an exorbitant quantity of the relatively expensive pigments to color the tile.

In elaboration of the facts outlined above, it should be borne in mind that the pitches are in themselves relatively opaque, and that stearin pitch has, by itself, relatively poor solubility.

I havesucceeded in making a material, useful as a base in the manufacture of mastic til-e and in the manufacture of protective coatings, in which a pitch of vegetable or animal origin is so combined with an additional low cost material as to form an elastic bodyywhich possesses such a relatively slight degree of opacity that it is readily and economically pigmented in all shades and colors, and which is soluble in the aromatic hydrocarbon solvents, and in the mixed solvents comprising aromatic hydrocarbon distillates and petroleum distillates.

This I do by subjecting a mixture of the pitch of vegetable or animal origin together with coalderived still residue to an oxidizing treatment conducted throughout a time period longer than that usually employed in the oxidation of the pitch taken by itself, and at a temperature lower than that at which such pitch is oxidized.

By pitch of vegetable or animal origin, as used herein, I mean a pitch the proximate origin of which is vegetable or a land or marine animal, as distinguished from pitches which are considered mineral, even though they may have remotely originated from vegetable or animal life.

The term still residue, as I use it herein, includes residual products resulting from the purification effected upon various fractions and derivatives of an oily material obtained from the distillation of coking of coal, which oily material is known as light oil.

The term light oil defines those fractional distillation products of coal which are obtained in standard coal by-product practice from scrubbers or in absorbing towers, and which contain a number of recoverable ingredients, among such being benzene, toluene, xylene, trimethyl benzene, ethyl benzene, coumarone, indene, cumene, cymene, hernmilithene, hydrindene and in gen ral methyl, ethyl, propyl and amyl addition or substitution products of the benzene ring group of aromatic chemicals. In subjecting the light oil to a purifying acid wash, and in distilling the light oil, liquid residue comprising lower polymers, reaction products, and materials of rela-' tively heavy molecular structure remains. Similar products are obtained from benzol stills, and from the acid purification of the light oil out known as crude solvent naphtha.

By subjecting the raw still residue and raw vegetable and animal pitch to oxidation, as a mixed batch, under certain appropriate conditions of oxidizing treatment, I am able to obtain the useful, elastic mixed product to which reference has been above made.

Still residue produced by any of the modes above described has been a substantially useless material, and has generally been considered as waste.

To describe an exemplary procedure by which the useful composite material is obtained, the pitch of vegetable or animal origin is first introduced into a treating vessel, which is provided with perforated coils for the distributed introduction of air through a liquid mass in the vessel, and which is provided with means for suitably heating the contents of the vessel, such as coils for the circulation of a heat-transferring fluid. As the pitch used as a starting ingredient is semisolid at normal room temperature, it is highly desirable that it be heated to a point of liquidity before the still residue, which is in liquid state, is commingled with it. To this end, the temperature of the pitch is initially raised to a point substantially above the melting-point of the pitch.

After the pitch has been rendered liquid by being raised to a temperature above its meltingpoint, the liquid still residue is introduced into the treating vessel, and is agitated with pitch to form a mixed liquid batch. The introduction of the air is then effected, while maintaining the batch at a temperature adequate to keep it in liquid condition suitable for the dispersion of air ther-ethrough. As the pitch exhibits a tendency to thicken, it is desirable that the treating temperature should at no stage of the process be much lower than 200 F., and that the air should be introduced under a pressure sufficiently high to insure its thorough dispersion through the batch. I have found that, with a blower and connections capable of delivering air to the treating vessel in good volume, efficient oxidation of a batch which is maintained adequately liquid is obtained.

After a relatively short period of oxidizing treatment, desirably after a period of treatment no longer than two days, the temperature of the pitch undergoing treatment is substantially raised, being, for example, raised to a temperature approximating 225 F. During the remaining treatment, which I have found it desirable to continue through an additional period not substantially less than two days, the temperature is raised to a point of from 250 F. to 300 F., in accordance with the degree to which oxidation of the pitch proceeds.

As a less convenient alternative to preheating the pitch to the point of liquidity, the pitch in semisolid condition may be introduced into a vessel simultaneously with the liquid still residue, and the two may be commingled by agitation under temperature conditions adequate to soften the pitch to a point at which it is a liquid miscible with the still residue.

My invention springs primarily from an appreciation of the facts that coal-derived still residue is a material possessing in marked degree the quality of chemical unsaturation, and that a mixture of the still residue and the pitch may by simultaneous oxidation be greatly increased in melting-point and viscosity, and substantially lowered in iodine value, to provide a composite body in which the oxidized pitch and the oxidized still residue are compatible, which has the melting point of a homogeneous mass, and in which the still residue has imparted to the mixed body substantial transparency in solution and in a film. I have also discovered that, as these starting materials are oxidized together, the mixed product has an elasticity and adhesion substantially greater than that possessed by the oxidized pitch alone, or possessed by a mixture of the oxidized pitch with those hardening materials with which it has previously been combined.

In the conduct of my process, in accordance with a typical procedure as above outlined, a treatment of approximately four days, conducted at a final temperature not substantially lower than 250 F. and not substantially higher than 300 F., gives a pitchy, elastic material having a melting-range of from 130 F. to 200 F., the material retaining its elasticity under ordinary atmospheric temperatures lower than its meltingpoint, and retaining its elasticity under heating up to the approximate melting-point.

Elevation in the melting-point of the product is obtainable by increasing the ratio of still residue to pitch in the mixed batch which is subjected to treatment; While a mixture comprising equal volume of still residue and vegetable or animal pitch gives, when subjected to the treatment above described, a product having an average melting-point approximating 160 F., a mixture comprising more still residue than pitch, such for example as a mixture comprising 2 volumes of still residue and 1 volume of pitch, gives a product of substantially higher melting-point up to the maximum of approximately 200 F. noted above. With either proportion of the ingredients the same approximate temperatures, and the same approximate duration of treatment, are employed; the increased melting-point, attendant upon the greater proportional inclusion of still residue, being attributable to the higher quantitative addition of oxygen of which the still residue is susceptible.

By further increasing the ratio of still residue to pitch, I have obtained a product having a melting-point as high as 225 F. At that point solubility in the aromatic hydrocarbon solvents declines rather abruptly.

The qualities of light color and relatively high melting-point are not obtained if the pitch is included in a volume substantially greater than the volume of the still residue.

A treating temperature of 300 F. may be given as a maximum practical temperature to which the mixed batch may be raised during;

treatment without distilling and blowing oif a substantial proportion of the lighter components of the still residue from the batch, and without substantially detracting from the transparency of the resultant mixed product.

It may be noted that the temperature under which the mixed batch is treated is raised progressively during the continuance of the treatment. This is for the reason that, as oxidation proceeds, a high temperature is requisite in order to maintain the batch adequately liquid for the dispersion of air therein. It is possible for the reason that the lighter components of the still residue, having initially the highest degree of unsaturation, are those most affected by oxidation and thereby acquire in the initial stages of the process a stage of oxidation rendering them less readily vaporizable. A temperature substantially higher than 300 F., by depriving the batch of the lighter still residue components, tends to produce a resultant material of impaired elasticity. While I prefer to begin treatment at a temperature approximating 200 F., it is possible initially to blow air through the mixed batches containing more than an equal quantity of still residue at a temperature as low as 160 F. The critical temperature below which oxidation is not effected to a substantial extent by blowing appears to be at, or slightly above, the point of 160 F.

It has been noted above that the mixed elastic product is soluble in aromatic hydrocarbon solvents and in mixed solvents comprising aromatic hydrocarbon distillate and petroleum distillate. This relatively good solubility is due apparently to the formation of a mutual solution of the still residue and the pitch components of the product in their final solid state. If the pitch used is stearin pitch, the solubility of the mixed product is substantially better than that of the pitch taken by itself.

To produce a modified pitch having a meltingpoint lower than that obtained by the exemplary procedure given above, which exemplary procedure may be considered a mean, or standard, procedure, I obtain this result by discontinuing the process at a point short of the ultimate or final conditions given as examplary, rather than by severe reduction in the pitch content of the mixture below a point of volumetric equality. Thus by shortening the period of treatment, I am able to obtain a modified pitch of selected melting-point down to slightly above normal room temperature.

Utility is found for modified pitch of selectively varied meting point, since for each melting point the modified pitch acquires substantial enhancement in one or more of the qualities of elasticity, transparency, and adhesion over the pitch taken by itself, either as raw or as blown. Thus the pitch having a melting-point from around F. down to slightly above normal room temperature is a desirable ingredient of adhesive compositions. The modified pitch having a meltingpoint of from 100 F. to F. is a desirable ingredient of roofing compositions and coating compositions, and is'a particularly desirable ingredient in rubber containing molding compositions. The pitch, as possessing a melting point in the neighborhood of 120 F. is of specifically great utility as an ingredient in baking films such as those used in the electrical industry for motor coatings, conduit coatings, and insulation coatings. As previously noted, the modified pitch, as melting within the higher ranges, has specifically high utility in mastic tile, linoleum, and the like, as well as utility in coating compositions generally considered.

I claim as my invention:

1. The herein described method of producing a composite pitchy material relatively light in color and transparent in solution and in a film, which is solid at normal room temperature and the components of which are mutually compatible, which comprises oxidizing in admixture pitch of non-mineral origin and liquid aromatic still residue from the purification and distillation of coke-oven light oil distilling over before tar in the by-product coking of coal, by dispersing gaseous oxygen through the mixture during an extended treating period, of the order of about 2 to 4 days of simple air dispersion through the mixture, while supplying to the mixture heat adequate to maintain it at a progressively increased liquefying temperature within the approximate range of F. to 300 F.

2. The herein described composite pitchy product comprising an aromatic still residue from the purification and distillation of coke-oven light oil distilling over before tar in the by-product coking of coal and pitch of non-mineral origin in oxidized condition and in mutual compatibility, said pitchy product being an elastic and thermoplastic body of relatively light color, solid at normal room temperature and transparent in solution and in a film.

3. The herein described method of producing a composite pitchy material relatively light in color and transparent in solution and in a film, and the components of which are mutually compatible, which comprises oxidizing in admixture pitch of non-mineral origin and liquid still residue from the treatment of coke-oven light oil by dispersing gaseous oxygen through a mixture of the pitch and still residue in which the volume of the still residue is at least equal to the volume of the pitch, and continuing the oxidation treatment to a stage at which the resultant mass has a melting-point within the approximate range of 160 F., to 225 F. while supplying to the mixture heat adequate to maintain it at a progressively increased liquefying temperature within the approximate range of 160 F. to 300 F.

4. The herein described composite pitchy product comprising an aromatic still residue from the purification and distillation of coke-oven light oil distilling over before tar in the by-product coking of coal and pitch of non-mineral origin in oxidized condition and in mutual compatibility, the volume of still residue in the product being at least equal to the volume of pitch therein, said pitchy product being elastic, being transparent in solution and in a film and having a meltingpoint within the approximate range of 160 F. to 225 F.

FRANK W. CORKERY. 

